General Characteristics• All have jointed legs
• Evolved from annelids (segmented worms)
• All have an exoskeleton made of chitin
• All have bilateral symmetry
WOW BEHAVIOR!• All molt- shed skin to allow for growth (lobster
example)
• Spiders molt too
Body Arrangement• All have 3 body segments – head, thorax
and abdomen
Arthropods all have an open circulatory system
“Blood” is confined to vessels for only a small portion of it’s circuit through the body.
FIVE CLASSES
• Centipede – one pair of legs per segment
• Millipede- two pair of legs per segment
• Insects- 3 pair of legs per thorax
• Arachnids- 4 pair of legs per thorax
• Crustaceans-5 pair of legs per thorax
Legs• Centipedes have 1
pair of legs per body segment.
DefensesHave large
poisonous fangs on their first appendages.
Centipede• Name means 100 feet. Do
they have 100 feet?
Centipedes• Have longer
antennae than other animals in the same class.
• Antennae are sensory organs, used for touch and smell
Feeding • Usually are
carnivorous, eating other arthropods
• Eat snails, slugs, and worms
Millipedes• Millipedes have 2 pair
of legs per segment.• Body has many
segments; as many as 100
Millipedes• Generally not
poisonous to humans
MillipedesName means 1000 feet. Does it have 1000 feet?
Millipedes• Millipedes spit
cyanide acid at prey.
Insects have 3 pairs of legs on their thorax
INSECTS undergo metamorphosis• Complete metamorphosis:
– Egg– Larvae– Pupa– adult
INSECTS undergo metamorphosis• Incomplete metamorphosis:
– Egg– Nymph– adult
Insects have 3 simple eyes between two compound eyes
Insects breathe through holes in their sides (usually the thorax) called spiracles
Many insects have camouflage
Insects mimic environment
Flight was an evolutionary advantage to insects• Damselfly goes from water to flight
Common blue damselfly
Drosophila flight
The miraculous honey bee!• Honey bees and relationship to humans
Wild and wonderful
Praying Mantis at the snake buffet
Weevil family
Amazing Mantis!!
Wild and wonderful
Monarch butterfly
Swallow tail species
Viceroy butterfly
Arachnid Includes
Spiders
Mites
scorpions
Arachnids have 4 pairs (8)of legs
All spiders have 2 pair of mouthparts
Spiders have fangs
Arachnids breathe by book lungs
Horseshoe Crabs are more closely related to arachnids then to crustaceans.
Malpigian tubules are used as kidneys to filter the “blood”
Arachnids produce a strong elastic silk from spinerettes to build a web to capture their prey
Cephalothorax Cephalothorax is the head attached to the thorax.
VisionOnly have simple eyes
Arachnids have poison to kill their prey
Brown Recluse
Arachnid feedingArachnids use enzymes
to dissolve food before ingestion.
Camel Spider
Trick photography
Real spider
Crustacean• Crustaceans all
have a cephalothorax
• Examples are crayfish, shrimp, lobster, and crabs
Most are aquatic• EXCEPT – rolly polly (pill bugs)
LocomotionHave 5 pairs of
appendages
Crustaceans have a special appendage used for swimming called a swimmerets
Green GlandHave an organ called
the green gland: which regulates the amount of salt and water in the body
Carapace – hard outer shell – protects inner organs
Amount of Legs• All crustaceans have five pair of appendages• And crustaceans have two pair of antennae
General Information• Crustaceans breathe
though gills• Mostly scavenge for
food
Some have a long appendage called a
telson-tail•